linux-kernel - Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

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Message-ID: <20250225181331.frmfumf4b5ctfbsm@jpoimboe>
Date: Tue, 25 Feb 2025 10:13:31 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Weinan Liu <wnliu@...gle.com>
Cc: indu.bhagat@...cle.com, irogers@...gle.com, joe.lawrence@...hat.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-toolchains@...r.kernel.org, live-patching@...r.kernel.org,
	mark.rutland@....com, peterz@...radead.org, puranjay@...nel.org,
	roman.gushchin@...ux.dev, rostedt@...dmis.org, will@...nel.org
Subject: Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

On Tue, Feb 25, 2025 at 01:02:24AM +0000, Weinan Liu wrote:
> On Mon, Feb 10, 2025 at 12:30 AM Weinan Liu <wnliu@...gle.com> wrote:
> > I already have a WIP patch to add sframe support to the kernel module.
> > However, it is not yet working. I had trouble unwinding frames for the
> > kernel module using the current algorithm.
> >
> > Indu has likely identified the issue and will be addressing it from the
> > toolchain side.
> >
> > https://sourceware.org/bugzilla/show_bug.cgi?id=32666
> 
> 
> I have a working in progress patch that adds sframe support for kernel
> module.
> https://github.com/heuza/linux/tree/sframe_unwinder.rfc
> 
> According to the sframe table values I got during runtime testing, looks
> like the offsets are not correct .
> 
> When unwind symbols init_module(0xffff80007b155048) from the kernel 
> module(livepatch-sample.ko), the start_address of the FDE entries in the
> sframe table of the kernel modules appear incorrect.
> For instance, the first FDE's start_addr is reported as -20564. Adding
> this offset to the module's sframe section address (0xffff80007b15a040)
> yields 0xffff80007b154fec, which is not within the livepatch-sample.ko
> memory region(It should be larger than 0xffff80007b155000).

I assume kpatch create-diff-object needs to copy over a subset of the
.sframe section.  Similar to what kpatch_regenerate_orc_sections() does.

-- 
Josh